This invention relates generally to a portable apparatus that can be selectively moved to the site of a concrete pad of the type that is commonly used to support equipment and structures--including transformers, switching equipment, pumps, generators and similar heavy equipment; more specifically, it relates to an hydraulically operated apparatus that can be utilized to raise an edge of a concrete pad without the necessity of first removing whatever heavy equipment is installed on the pad.
There are many instances in which time and natural forces (including erosion) have an adverse effect on concrete pads (i.e., small slabs) of the type that are widely used to support heavy equipment. Equipment such as transformers, electrical switches, generators, air conditioning compressors, etc., are frequently placed on top of such concrete pads in order to provide stability for the equipment. However, a concrete pad that was installed or poured so as to be level will not necessarily remain level over a period of years. It is common, therefore, to visit a remote piece of equipment and find that soil erosion or repetitive freezing and thawing has caused the supporting soil to have failed in its job of maintaining the slab in a level condition. Because transformers and the like have cooling oil that is designed to maintain the transformers at a desired temperature, anything that causes a transformer to tilt more than a very modest amount can contribute to uneven cooling and perhaps inordinate temperatures that might even cause a transformer to fail. Obviously, then, it would be desirable to restore a concrete pad of the type described herein to a level condition. And if possible, the restoration should be accomplished without taking the transformer out of service or requiring that it be removed from the pad in order to lighten the load that must be lifted.
It is true that lifting devices have been developed and used in other applications. For example, U.S. Pat. No. 4,591,466 to Murray and Bright entitled "Method For Positioning And Stabilizing A Concrete Slab" teaches an apparatus for elevating a portion of a concrete slab when the slab has a hole with a substantial quantity of structurally sound concrete around it. The presence of the structurally sound concrete around the hole is necessary because the Murray and Bright apparatus relies on placing a driving apparatus on top of the slab and using the slab as an anchor to obtaining resisting forces as a series of tubular shafts are driven into the ground under the slab. A similar device is shown in U.S. Pat. No. 4,800,700 to May entitled "Method and Apparatus For Lifting And Supporting Slabs." The May technique involves cutting an elongated hole into a concrete slab and using a special lift plate that is similarly elongated. However, there is no teaching in either of the patents of a technique for approaching the edge of a small slab and pushing directly against the earth instead of pushing against the slab that is to be lifted.
Another device of the prior art is shown in U.S. Pat. No. 4,100,714 to Stith, Jr. entitled "Method Of Positioning And Supporting A Machine." However, the Stith technique requires the presence of an existing concrete foundation against which lifting forces may be exerted in order to lift the edge of a heavy machine by relatively small amounts. In situations where there is no concrete foundation to push against, it would be impossible to utilize a Stith device.
It is also known to elevate the side or corner of a house when a concrete foundation has shifted. But anything that has the size such that it could lift the corner of a house would likely be of such bulk and shape as to require that it be mounted on the rear of a truck or special-purpose vehicle. Regrettably, there is seldom enough room around many transformers and the like to permit a truck to be backed up to a work site. Accordingly, there has remained a need for a portable device that can be handled by two or three men and that has the capacity to lift several hundreds or thousands of pounds. It is an object of this invention to provide such a portable apparatus, and to teach the method of using it to restore concrete pads easily and in a short period of time.
It is a further object to provide an apparatus that can be operated to drive a shaft vertically into the ground even when the terrain around the shaft is not horizontal.
Still another object is to provide an apparatus that is capable of using readily available reinforcing rod as the supporting shaft for a lifting device.
These and other objects will be apparent from a close reading of the specification and claims that follow, together with reference to the several figures of the drawing that are provided herewith.